An EnMAP .tar.gz archive contains one or more .ZIP sub-archives, each containing one EnMAP product. Currently, when opening a multi-product archive or directory, xarray-enmap simply opens the first product and ignores the rest. We should consider better ways to handle this. Adding a lazy `open_datatree` implementation to `EnmapEntrypoint` might be the most appropriate solution. Additionally or alternatively, we could add a filter parameter to the `open_dataset` implementation to allow the caller to select a known, specific sub-archive, e.g. by name or substring thereof.